This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Patients with diabetes benefit from self glucose monitoring. Current techniques for performing self glucose monitoring require piercing the skin with a lancet to obtain a droplet of blood. Because of this, they are associated with some discomfort and a small risk of infection. This study tests whether it is possible to monitor glucose non-invasively by measuring glucose levels in fluid that is collected from the air that is expired during normal breathing (this fluid is called the exhaled breath condensate or EBC). This proof of concept study will proceed in two phases. The first phase will attempt to demonstrate that glucose can be measured in EBC and that it is correlated with blood glucose measurements. EBC will be collected using a standard non-invasive apparatus in volunteers with diabetes and non-diabetic controls. EBC glucose will be compared to capillary blood glucose measurements (finger stick method) and plasma glucose measurements. If this phase successfully demonstrates that glucose can be measured in EBC and that it reflects capillary and plasma glucose levels, then the second phase of testing will be performed. In the second phase, the response of EBC glucose to physiological changes in plasma glucose will be assessed. EBC will be collected before and during a standard 75-gram oral glucose tolerance test in patients with diabetes and non-diabetic controls. The time course of changes in EBC glucose will be compared to those of capillary and plasma glucose levels. The information gathered from this study will provide information that may lead to the development of a non-invasive glucose monitor, based on the principle of EBC glucose measurements, for patients with diabetes.